Washable paper



Patented May 11, 1937 UNITED STATES WASHABLE PAPER Robert A. Voet, Oak Park, 11]., assignor to United Wall Paper Factories, Inc., Jersey City, N. J., a corporation of Delaware No Drawing.

Application July 2'7, 1934,

Serial No. 737,207

2 Glaims.

My invention has to do broadly with arts wherein a protein such as casein, albumin, glue, and the like are used. Sucharts, for example, include the coating of paper and the like, formation of films, webs and binders for pigments, the

application of wood-joining glues, etc. An important field in which protein, particularly casein, binders are used is in the manufacture of waterproof wall paper, wherein casein is usually used as a binder for the pigment and also as a waterproof coating for the printed paper.

It has been customary for a long time in using such adhesives to harden or set them by means of formaldehyde, either in the form of a gas or as a strong aqueous solution,which has been incorporated with, sprayed upon, or otherwise applied to the solubilized or solubilized and dried protein. However, the use of formaldehyde has always been highly objectionable from a manufacturing standpoint because of the irritating effect of the gas on the mucous membrane, eyes and epidermis of workmen. This condition has required considerable expense to-the manufacturer for equipment designed to reduce the discomfort of workmen as much as possible.

I An object of my invention is to produce a hardening or setting agent for protein materials of the I type referred to above which is as effective as formaldehyde and at the same time avoids the 0 irritating effects on the workmen above referred to. I have been successful in evolving such a setting or insolubilizing agent which completely eliminates these disadvantages of formaldehyde and is suificiently inexpensive tobe commercially 5 attractive.

I have found that a solubilized protein may be insolubilized, i. e., set or hardened, by means of a solution containing formic acid, combined with I am aware that aluminum acetate has previously been suggested as a hardening agent for solubilized proteins. However, this material leaves a distinct acetic acid (vinegar) odor on the hardened and dried material. It is, therefore, objectionable. In accordance with myinvention, on the other hand, substantially no odor remains.

PREPARATION or HARDENING SOLUTION Example I The following is a preferred example of a hardening or setting solution prepared in accordance with my invention: e To 20 parts of water at 75 C., add 5 parts of aluminum formate. When this has completely dissolved, dilute with 75 parts of cold water. Then, if it is necessary to change the acidity phase of the solution, this can be done by careful use of a suitable alkali such as sodium hydroxide, but a careful check should be made with a sensitive type of pH indicator. For best results, the pH value should not exceed 5.5.

Example II Other examples According to the general methods above described, other chemicals may be substituted for ;the materials specified in the two preceding examples. Among such other chemicals which may be employed, are those set forth in the following table of examples, commercial grades of the speci- 40 an alkalme reacting metal or metalloid, such as fled chemicals being referred to in eachinstance:

Example Parts by Parts by Water pH 0! parts by final 45 3 Potassium formate.-.. 5 Aluminum sulfate... 2 93 4.8

4 Potassium formats.... 5 90% formic acid. lg 94% 4. 8

5 Magnesium formats..- 5 Aluminum sulfate.-- 2 93 4. 9

6 Magnesium formats... 5 90% formic acid... M 94% 4. 9

7 Calcium formats 5 Aluminum sulfate... 2 93 4. 9

8 Calcium formate.. 5 90% formic acid.. )6 94% 4. 9

9 Barium formate... 6 Aluminum sulfate... 1% 93% 4. 8

5Q 10 Barium formate 5 90% formic acid. $4 94% 4. 8

11 Sodium formate..- 5 90% formic scid 6 94% 4. 8

12 Aluminum formate..-- 5 Sodium carbonate..- 1% 93% 4. 9

13 Ammonium formats.-- 5 Aluminum sulfate... 1 93% 4.9

14 Ammonium formats... 5 90% formic acid i 93% 4. 9

55 aluminum, sodium, potassium, calcium, magnesium, barium, or ammonium, said solution being made slightly acid; 1. e., acid down to a limit of approximately pH 4.8, and preferably between the approximate limits of 5.5 and 4.8. The acid- 00 ity is preferably produced by the S04 radical.

APPLICATION or Hsnnnmno SOLUTION T0 MANUFAC- TUBE-Oil WATER-PROOF WALL PAPER To form the solubilized protein binder, soak 20 parts of dry casein and '75 parts of water for half an hour. Then while agitating the mixture,

raise the temperature to 48 C. At this point, add 4 pounds borax in suflicient amount of water to dissolveit. When all lumps and undissolved particlesdisappear and the solution cools, it is ready for use by incorporating it with the other materials, such as clay, color pigments, bronze powders and dry mica to form the coating ma terial, and the color inks. It is usual to have the micasand bronzes pulped'beforehand with some type 'of a low starch content-gum, e. g., gum tragacanth, which tends to act-both as a dispersing agent and a colloidal suspender.

The paper web is formed with a filler containing solubilized casein, and is partially or wholly dried in the usual way.

The coating material, e. g., clay, suspended in the protein binding agent above referred to, is

d spread evenly over one side of the web of paper and dried usually by passing it through a drying rack in festoons where ducts supplyhot air which drives off the moisture in the coating,

The degree of water resistance obtained by using this hardening agent is of first-class quality and, in addition, any possible effect upon the paper fibers or printed colors is more negligible than when formaldehyde or formaldehyde and alum in solution is used.

ALTERNATIVE E M BODI MENT Instead of applying the setting solution to the protein coating as described above, I may combine it with the protein in dry form and dissolve as required. The following example is illustrative:

Seventy parts of 30-mesh casein, 10 parts borax, parts hydrated lime, 5 parts aluminum formate, and 5 parts sodium. fluoride are thor- 50 oughly mixed and passed through a 30-mesh screen. The dry mixture thus produced may be shipped in dry form and placed in solution as needed. For the quantities given above, add 400 a retarder to prevent immediate precipitation of the protein by the aluminum formate.

Various other modifications of my invention may suggest themselves to those skilled in the art without departing from the spirit of my invention and, hence, I do not wish to be limited to the specific embodiments disclosed herein, except to the extent indicated by the appended claims, which are to be interpreted as broadly as the state of the art will permit. Methods will be obvious to those skilled in the art, without giving additional detailed examples, for preparing other hardening solutions embodying my invention and including one or more of the metals or metalloids specified above, and adjusted to the specified acidity.

I claim as my invention:

1. A method of preparing an article of the class described, comprising treating a paper web with a coating containing solubilized casein as a potentially water resistant binder, at least partially drying the paper web, printing upon said web with an ink also containing 2 potentially water resistant casein binder, and treating said web to fix said binders and render the surface of the paper water resistant by means of a solution of a formic acid salt of a member of the group consisting of alkali and alkaline earth metals, ammonium and aluminum, said solution having been adjusted to a pH value between the approximate limits of 4.8 and 5.5.

2. A method of preparing water-resistant paper comprising treating a paper web with a coating composition containing a solubilized casein binder, at least partially drying said web, and

- insolubilizing said binder with a solution of a formic acid salt of a member of thegroup consisting of alkali and alkaline earth metals, aluminum and ammonium, said solution having been adjusted to a pH value between the approximate limits of 4.8 and 5.5.

ROBERT A. VOET. 

